This project proposes to investigate the various aspects of shock, including: 1. Assessment of the use of prostaglandin E1 in the treatment of hemorrhagic shock in dogs. 2. The effect of administration of various energy substrates during the "normovolemic" phase of hemorrhagic shock on biochemical changes and on survival. 3. The relationship of changes of tissue metabolites including ATP, lactic acid, pyruvic acid and lysozomal enzymes to the response of hemorrhagic shock to therapy. The affect of fluid overload on dogs at various levels of cardiac function.